I wouldn't breed them. If you like them both and have gallonage to raise them to adulthood keep them. Maybe sell one off down the road, but I highly reccomend separating them before the weaker one gets killed!
I had this problem. They were 1 1/2" at best, thought they would be ok till I could at least tell which would be better looking. Went to work at the firehouse and came home the next morning and go figure, they better looking one was nose down on the bottom.